More and more the processing power is being required of all types of microelectronic modules and systems. A multi-chip module is a device that may provide the required processing power. A multi-chip module is a device containing a number of interconnected integrated circuits (i.e., dice) in one package. There are three types of multi-chip modules (i.e., laminate, ceramic, and deposition).
A laminate multi-chip module includes dice connected using various pre-fabricated laminate layers. A laminate multi-chip module can be conformal, but it may not be the smallest multi-chip module that can be made.
A ceramic multi-chip module includes dice on pre-fired (i.e., soft) ceramic tape known as "green tape." The combination is then fired to form a rigid device. The ceramic multi-chip module can be smaller than a laminate multi-chip module, but it is not conformal.
The last class of multi-chip module is a deposition multi-chip module. A deposition multi-chip module consists of standard-thickness dice placed on a supporting substrate. Since standard-thickness dice may form a surface topology that is too irregular to reliably accept a subsequent layer of interconnect, a planarization step is required to smooth the resulting irregular surface topology. There are at least three methods to planarize integrated circuits on a substrate. The first method is to place each die in its own well in the substrate and deposit a dielectric material in the remaining spaces in the wells. The second method is to place the dice onto a flat substrate, deposit a planarizing dielectric material over the dice and the substrate, and smooth the dielectric. The third method is to place the dice on a flat substrate and place a prefabricated stencil (commonly referred to as a window-frame) in the remaining spaces between the dice. A dielectric layer is deposited or laminated over the integrated circuits. Vias are cut into the dielectric in order to contact the dice. At least one thin-film interconnect layer is deposited over the dielectric layer. The deposition multi-chip module can be the smallest of the three classes of multi-chip modules, and if the multi-chip module is thinned after fabrication of the interconnect layers, it can be conformal as well.
Present laminate and deposition multi-chip modules suffer from at least five problems. The first problem is that standard-thickness dice are presently being used. The thinnest and most conformal multi-chip module cannot be realized using standard-thickness dice. The second problem is that a planarizing dielectric layer is deposited or laminated onto the dice prior to the deposition of the first interconnect layer. Again, the thinnest and most conformal multi-chip modules cannot be realized by using a planarizing dielectric layer between the dice and the first interconnect layer. The third problem, for those who attempt to thin the deposition multi-chip module after depositing the interconnect layers, is that the dice may be damaged during the thinning process and the manufacturing yield for the multi-chip module will suffer. There is presently no way of repairing a deposition multi-chip module after the interconnect layers have been deposited. Therefore, the manufacturing yield for the prior art methods of making thin conformal multi-chip modules is not as high as it could be. The fourth problem is that flexible multi-chip modules which use standard thickness (i.e., rigid and inflexible) dice separated by flexible interconnect must leave adequate space between dice so that bending of the interconnect can occur at these joints. Since the dice are standard thickness, bending occurs only at these joints. The space necessary for these joints is entirely eliminated by the present invention. The fifth problem is that flexible multi-chip modules which use standard thickness dice separated by flexible interconnect spaces cannot flex along an axis diagonal to the direction of the spaces. The flexibility of the thinned dice in the present invention allows flexibility in any direction. These five problems are corrected by the present invention.
U.S. Pat. No. 5,401,688, entitled "SEMICONDUCTOR DEVICE 0F MULTICHIP MODULE-TYPE," discloses a laminate multi-chip module that uses standard thickness integrated circuits. U.S. Pat. No. 5,401,688 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. Nos. 5,432,677, entitled "MULTI-CHIP INTEGRATED CIRCUIT MODULE," and U.S. Pat. No. 5,386,623, entitled "PROCESS FOR MANUFACTURING A MULTI-CHIP MODULE, each disclose a method of making a deposition multi-chip module by placing each standard-thickness die into its own well in a substrate. These two patents do not result in a multi-chip module that is as thin or as conformal as a multi-chip module produced by the method of the present invention. U.S. Pat. Nos. 5,432,677 and 5,386,623 are hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 5,373,627, entitled "METHOD OF FORMING MULTI-CHIP MODULE WITH HIGH DENSITY INTERCONNECTIONS," discloses a method of making a deposition multi-chip module where standard-thickness dice are placed on a dielectric layer deposited onto a flat substrate. The substrate is later removed, but even then, because of the remaining dielectric layer and the standard-thickness dice, the resulting multi-chip module is not as thin, conformal, or as high-yielding as a multi-chip module produced by the method of the present invention. U.S. Pat. No. 5,373,627 is hereby incorporated by reference into the specification of the present invention.